In recent years, electronic devices such as information terminals and devices such as instruments provided in a vehicle such as an automobile widely use a liquid crystal panel as a display panel for displaying an image or information. Furthermore, this type of display device is equipped with a backlight device (lighting device) that supplies light to the liquid crystal panel, besides the liquid crystal panel.
For example, as described in Japanese Unexamined Patent Publication No. 2013-149559, an edge-light type (or sidelight type) backlight device that includes a light guide plate including a transparent plate-like member, and a light source (e.g., LED) that is arranged so as to oppose an end surface of this light guide plate has been known as a backlight device. Light emitted from the light source of the backlight device enters into the light guide plate from the end surface (hereinafter, referred to as the light incidence surface) of the light guide plate opposing the light source. Furthermore, the light propagates within the light guide plate, and is emitted from the plate surface on the front side (hereinafter, referred to as the light emission surface) as planar light. Such an edge-light type backlight device has an advantage in that the device can be made thinner as compared to other types (e.g., direct type).
However, the edge-light type backlight device as described in Japanese Unexamined Patent Publication No. 2013-149559 has a problem in that, when a hole is provided in the plate surface, the path of light that enters into the light guide plate from the light incidence surface and travels straight to an opposite surface of incidence that is positioned on the opposite side of the light incidence surface, is interrupted by that hole, and thus luminance unevenness is caused due to decreased luminance in a region positioned on the opposite surface of incidence side with respect to the hole.
In order to solve such luminance unevenness, a configuration in which a light source is provided also on the opposite surface of incidence side can be conceived. However, such a configuration results in a complicated configuration for arranging light sources, and consequently increases the size and cost of the backlight device.